Method for making elastomeric articles

ABSTRACT

A method for molding shaped silicone elastomeric articles from room temperature curable silicone compositions, which are practically not suited to being processed using extrusion techniques, is provided. The method enables the room temperature curable silicone composition to cure in a predefined shape ( 6 ) into which it is introduced to form a shaped silicone elastomeric article. The articles may be, for the sake of example, suitable for use as spacers for insulating glass units (IGUs).

This disclosure relates to a method for making elastomeric articles fromroom temperature curable silicone compositions, which are practicallynot suited to being processed using extrusion techniques. The articlesmay be, for the sake of example, suitable for use as spacers forinsulating glass units (IGUs).

It has been standard practice for many years to form transparent unitssuch as insulating glass units (IGUs) consisting of two, three, or moreglass panes with each adjacent pair of panes spaced apart using asuitable spacer and sealant combination applied by way of an “edge seal”process. The edge seal process provides a means of spacing adjacentpanes apart whilst also providing a seal extending around the peripheryof the inner facing surfaces of the glass panes to define asubstantially hermetically sealed insulating space between the glasspanes. In such an edge seal system a spacer is provided to space apartthe panes of e.g., glass. Whilst spacers may self-adhere to the glass,most do not in which case satisfactory adhesion of the spacer to theglass panes is conventionally provided by way of a primary sealant. Thespacer and primary sealant combination is designed to be moisture,vapour and/or gas impermeable, to prevent moisture or water vapourentering and condensing in the inner cavity of the unit and, in case ofa gas filled unit, avoiding escape of gas from the unit. The so-called“primary” sealant may be e.g., a “butyl sealant” e.g., a polyisobutylenerubber-based material which is utilised to bond non-self-adhesivespacers e.g., metal spacers to the glass panes and to employ a secondarysealant bonded to the panes around the spacer.

The aforementioned secondary sealant, often a silicone sealant, isprovided at the periphery of the insulating glass unit between the edgeportions of the glass panes, such that the layer of secondary sealant isin contact with external surface of the spacer. The secondary sealantserves to promote the integrity of the bond of the self-adhered spaceror primary sealant by minimising the strain imposed on it due toexternal factors such as fluctuations in ambient temperature, barometricpressure, or wind pressure.

A wide variety of spacers have been proposed. Currently, more commonlynon-adhesive spacers are utilised. These may include foamed plasticsmaterials, for example a silicone foam or a polyolefin foam such as anethylene propylene diene terpolymer foam; a mastic, for example apolyisobutylene mastic, containing a reinforcement which helps to keepthe glass sheets the required distance apart when the insulating glassunit is assembled. Alternatively, the spacers may be made from rigidmaterials such as metals like aluminium or stainless steel or rigidplastic materials such as, for the sake of example, polycarbonate orpolymethylmethacrylate (PMMA). These rigid spacers may be constructed tobe hollow enabling desiccant to be introduced into the hollow regionthereof.

For example, in one typical form of insulating glass unit construction,the edge seal comprises a hollow metal or plastic spacer element adheredto the inner facing surfaces of the glass panes by a primary sealant toprovide a primary hermetic seal. The hollow spacer element is filledwith a desiccant material, which is put in communication with theinsulating space between the glass panes to absorb moisture therefrom inorder to improve the performance and durability of the insulating glassunit.

Alternatively, self-adhering spacers may be utilised. These may includespacers made from thermoplastic materials and self-adhering siliconespacers such as those described in WO2018160325. During assembly of aninsulating glass unit having a self-adhesive spacer, the spacer isapplied as an elongate elastomeric “strand” which will adhere to theintended substrates with which it is to be used.

In use as a self-adhesive spacer for IGUs, the strand is applied onto afirst of two glass panes along its edge. The beginning and the end ofthe strand may be joined. The second glass pane is then placed directlyon top of the self-adhesive spacer the two panes are pressed togetheruntil they are a predetermined distance apart, equal to the width thatthe spacer is to have in the insulating glass unit, so that the strandof self-adhesive spacer is pressed against the glass panes and bonds thepanes together. A secondary sealant or alternatively a protectivecoating or the like may then be applied if deemed necessary.

However, whilst until now the elongate strands have generally beenprepared using an extrusion methodology the compositions described inWO2018160325, which are designed to be transparent, are unsuitable forextrusion techniques because they are condensation curable thermosettingmaterials which cure slowly and which have gel points which are notreached for at least several minutes from the start of the cure processand indeed in some instances the gel point is not reached for severalhours. For the avoidance of doubt by gel point we mean the time when tandelta (G″/G′) is 1 i.e., where G″ (the storage or elastic modulus inshear) and G′ (the loss or viscous modulus in shear) are equal. Thisrepresents the transition from a liquid to a solid material. Around thistransition point the material is behaving as a viscoelastic material,which will deform differently according to the level of the stress thatis applied to the material. Before the gel point, the material is verysensitive to any stress applied, which can induce flow thereof. Beyondthe gel point a low stress applied will induce reversible deformation,i.e., the material will return to its initial position after the stressis removed. The gel point of a material may be determined using severalalternative methods including, for the sake of example, by way of thetests in ASTM D4473-08 (2016).

The vast majority of non-adhesive spacers, self-adhesive spacers,primary sealants and/or secondary sealants utilised in edge-seal systemsare black, white or opaque or even otherwise coloured, thereby reducingthe area of the insulating glass unit through which light may pass.

There is therefore now a desire to produce transparent spacers for IGUsparticularly when vision through the IGU is important, e.g., commercialfridge applications. Incumbent solutions mostly use a rigid clearplastic such as a polycarbonate or polymethylmethacrylate (PMMA) spacerthat is fixed onto the glass via using a clear double-sided tape.However, this has a specific drawback, that of adhesion durabilitybecause as the plastic materials used are typically rigid, it haslimited movement capability and any movement during transport or use canlead to loss of adhesion and consequently moisture can enter the innercavity of the IGU leading to condensation and fogging.

The transparent silicone spacers described in WO2018160325 have muchbetter adhesion durability than that of the aforementioned rigid plasticspacers due to their better flexibility and to the fact that thechemical adhesion of the silicone to the glass is maintained, even afterprolonged periods of aging (e.g., high temperatures or hot waterimmersion).

As such there is a desire to manufacture elongate silicone moldedarticles suitable for use as spacers from room temperature curablesilicone compositions by means of a method which does not involve theneed for extrusion.

There is provided herein a method for molding shaped siliconeelastomeric articles from room temperature curable siliconecompositions, comprising:

-   -   (i) draping a film over a mold comprising two or more predefined        shapes to establish an evacuatable volume between the film and        each predefined shape in the mold;        -   (ii) applying suction to the evacuatable volume between a            first predefined shape of the mold and the film to establish            an at least partial vacuum within the evacuatable volume of            said first predefined shape, such that the film forms a            filmic inner lining conforming to the first predefined shape            of the mold;    -   (iii) additionally, applying suction to the evacuatable volume        between a second predefined shape of the mold and the film,        which second predefined shape, is adjacent to the first        predefined shape, to also establish an at least partial vacuum        within the evacuatable volume of said second predefined shape        and consequently also forms a filmic inner lining conforming to        the second predefined shape of the mold;    -   (iv) sequentially repeating step (iii) until each predefined        shape in the mold has an at least partial vacuum within the        evacuatable volume thereof and the film forms a filmic inner        lining conforming to each respective predefined shape of the        mold;    -   (v) introducing room temperature curable silicone composition        onto the filmic inner lining conforming to one or more        predefined shapes of the mold, which composition is designed to        flow sufficiently to conform to the predefined shape in the mold        into which it has been introduced; and    -   (vi) enabling the room temperature curable silicone composition        to cure in the predefined shape into which it was introduced to        form a shaped silicone elastomeric article.

The method described above is intended for use with materials which areimpractical to prepare via extrusion processes such as the roomtemperature curable silicone compositions described in WO2018/160325having gel points of from several minutes to several hours which aretherefore not sufficiently structurally resilient during the initialstages of the cure process to be used to prepare elongate “strands”.byextrusion. This is particularly the case if the composition once mixedhas a low enough viscosity to be flowable, a likely scenario whenminimal or no filler is present in the composition. Furthermore, thesecompositions cure via a condensation process over an extended period oftime e.g., from several hours to several days, e.g., 7 days or longer,typically by a condensation process.

For the avoidance of doubt a flowable room temperature curable siliconecomposition has a viscosity which is sufficiently low immediately priorto commencement of the cure process to visibly flowable under theinfluence of gravity and/or be even self-levelling. By structuralresilience we mean the ability to hold its structural form in theabsence of e.g., a mold or other form of support.

The method described above provides a suitable route for the manufactureof shaped silicone elastomeric articles e.g., elongate siliconeelastomeric articles from room temperature curable silicone composition.It is desirable to produce elongate silicone elastomeric articles withparallel sides, for example, to be used as spacers in insulating glassunits (IGUs) which avoids the need to rely on an extrusion process.Hence, the above method provides a means of producing shaped siliconeelastomeric articles, especially elongate silicone elastomeric articlese.g., spacers, from room temperature curable silicone compositions,which may be flowable at the commencement of cure. The articles e.g.,pre-cured spacers described in WO2018160325, are both self-adhesive andtransparent and as such this method, when using compositions asdescribed therein or similar compositions provides a means for themanufacture of self-adhesive transparent spacers, which once introducedinto insulated glass units provide the viewer with a better viewingcapability.

The method of the present disclosure utilises a mold and a film becauseit would be undesirable to leave the one or more predefined shapes inthe mold filled with room temperature curable silicone composition forthe whole cure period, unless deemed necessary, as potentially adhesionproblems between the elastomer and the mold walls might occur and as aconsequence would potentially result in damage to the elongate shape ofthe cured silicone elastomer articles when eventually removed from themold post cure.

The mold, as used herein, comprises two or more predefined shapes. Inone embodiment the two or more predefined shapes are two or moreelongate parallel channels, alternatively a series of elongate parallelchannels in a mold. In such an instance the predefined shape may be ofany suitable cross-section, but rectangular, alternatively squarecross-sections to provide cured or partially cured elongate siliconeelastomeric articles with at least two parallel sides are preferred. Forexample, in one embodiment, when the intended end use for the resultingcured articles is as spacers for IGUs, the parallel channels are formedby walls which are of a height greater than that desired for the moldedarticles, e.g., at least 5 mm higher than molded articles. The walls maybe of any suitable construction e.g., they may have rounded or sharpenededges.

The shaped silicone elastomeric articles can be designed to be of anydesired shape and size, i.e., in order to be suitable for their end use.In the case of elongate silicone elastomeric articles such as spacersfor IGUs they may for example, be 7.5 to 25 1mm wide, alternatively 10mm to 25 mm wide and 5 to 25 mm deep, alternatively 10 to 25 mm deep,alternatively 10 to 20 mm deep. The length of the elongate siliconeelastomeric articles can be anything up to the full length of thechannel in which it is being molded. Indeed, if required, after thecompletion of cure, the length of the article may be cut to size or cutinto multiple different lengths. However, for example the article may bee.g., from 0.5 to 3 m in length, alternatively from 1 to 2.5 m inlength.

When the or each predefined shape in the mold is an elongate channel,the elongate channel may have a rectangular cross-section oralternatively a square cross-section with a substantially horizontalbase, alternatively a horizontal base, a first side wall and a secondside wall. The first side wall and the second side wall aresubstantially vertical or vertical, parallel to each other and arepositioned approximately perpendicular or alternatively perpendicular tothe base.

Each of the two or more predefined shapes in the mold contain a seriesof openings designed to enable an at least partial vacuum to beestablished by evacuating air and/or other gases from the respectiveevacuatable volume created by draping the film over the respectivepredefined shape in the mold. The openings may be of any suitablecross-section but are typically of a circular, square or rectangularcross-section, alternatively a circular cross-section. When the holeshave a circular cross-section, they may have a diameter of from 0.5 to 3mm, alternatively 0.5 to 2 mm.

In one embodiment when the two or more predefined shapes are a series ofelongate parallel channels in the mold, each parallel channel having abase and a first and second parallel side walls at an angle ofapproximately 90° to the base, the openings are positioned at a setdistance apart along one or both side walls and/or in the base of thechannel. Alternatively, the openings are positioned a set distance apartin the corner(s) between the base and the first side wall and a setdistance apart in the corner(s) between the base and the second sidewall. The positioning of said openings are important as they ensure thatthe film conforms to the shape of the mold once suction is applied tothe evacuatable volume. Hence, in one alternative, the openings may be,or are equidistantly distributed along the length of each channel of themold to enable a consistent vacuum to be drawn along the whole length ofthe respective channel.

The suction applied causes a vacuum to be drawn through the openings toevacuate gases from the evacuatable volume of the pre-defined shape(e.g., channel) and consequently draws the film into the predefinedshape (e.g., channel). The film used is designed to conform to the shapethereof to create a filmic inner lining in the respective predefinedshape, e.g., channel. The vacuum drawn in any one predefined shape maybe drawn independently from vacuum in each other predefined shapes inthe mold. This may be achieved by having an on/off switch for vacuum tobe operated for each individual channel.

Any suitable type of vacuum generator may be used for the application ofa vacuum in the evacuatable volume of between a predefined shape and thefilm of a mold. For example, venturi tubes (using compressed air orwater flow) or vacuum pumps, One suitable vacuum generator from theabove list may be utilised per mold providing suitable switchingmechanisms are available to enable suction to be initiated in apredefined shape independent from all other predefined shapes in themold. Alternatively, if desired or deemed necessary, a separate vacuumgenerator may be utilised with respect to each predefined shape.

In one embodiment the mold may comprise a single unit having a mold partand a vacuum part wherein the vacuum part is connected to a suitablevacuum generator as described above and is designed to draw a vacuumthrough the openings in the respective predefined shape. Alternatively,the mold part and the vacuum part may be two inter-connectable partswhich, in use, are engaged in order for a vacuum to be applied into theevacuatable volume between the film and a predefined shape but enablingthe vacuum part to be disconnected as and when the vacuum is deemed nolonger required. Hence, the vacuum part may be detachable e.g., suchthat whilst the mold is being used to mold the final article during thelengthy cure period the vacuum part may be reused with additional moldswhich may be fixable placed on top of the vacuum part with the openingsaligned thereto to enable a vacuum to be drawn as described elsewhere.

The film utilised herein to form the filmic inner lining in thepreformed shapes of the mold may be any suitable film for such apurpose. Films were selected based on three main criteria:

-   -   (i) the ability to conform to the predefined shapes in the mold        via the method used herein without being damaged or stretched;    -   (ii) the avoidance for the need to heat the film to gain        adequate conformity thereof to the predefined shapes    -   (iii) being releasable from the self-adhesive silicone elastomer        article generate post-cure.

In one embodiment the film material used may be chosen with respect toits “wettability” by the room temperature curable silicone compositionto be introduced into the predefined shapes, in that it is desired forthe composition to have a minimal meniscus when the film is functioningas an internal layer of the mold, i.e., when the composition has flowedunder gravity into position the composition/air interface isapproximately horizontal. Suitable films of this type include, for thesake of example, polyethylene (PE) especially low-density polyethylene(LDPE), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE)and fluorinated ethylene-propylene (PEP). If desired said films may bemodified to incorporate additives such as, for the sake of example, slipadditives and/or anti-block agents. By wettability we mean the abilityof a liquid to maintain contact with a solid surface, resulting fromintermolecular interactions when the two are brought together. The abovewere found to be suitable because these films did not have a negativeimpact on the adherence properties of the spacer when applied on glass.It was found that some films depending on

(i) their film surface functional groups,

(ii) different surface species or

(iii) different orientation of the surface species could impact how thespacer adheres on glass post-cure. The film may be a release film.

The film is preferably highly flexible and has a film thickness of from10 to 100 μm, alternatively from 20 and 70 μm (thinner films tend tocrinkle whereas thicker films do not conform well onto surface).

The film used herein may be treated prior to use to enhance adhesion orother properties to the mold surface at room temperature and maintainits position even in the absence of vacuum. This may be by applicationof an adhesive such as a NUCREL™ acid copolymer adhesive product fromDow or a surface treatment (e.g., corona or plasma activation). In oneembodiment the surface of the film to be in contact with the moldsurface is corona or plasma treated prior to use as a means of enhancingthe conformability of the film to the predefined shapes in the mold.

When each predefined shape in a mold is an elongate channel aspreviously described, each channel in a mold has two ends. Both ends maybe fixed in place or may alternatively be open-ended or one end is fixedin place and the second end is open-ended. Whichever is the case, aslidable guide may be utilised in order to vary the length of theelongate predefined shape (e.g., channel). It may also act as a guidefor the film to ensure it retains its desired position because it wasfound to be a significant challenge to maintain the position of the filmin each respective predefined shape of the mold to avoid stretching ofthe film and/or non-conformity thereof to the predefined shape resultingin causing a negative effect on the shape of the elongate siliconeelastomeric articles resulting from curing room temperature curablesilicone composition in the predefined shape (e.g., a channel). The filmis required to form a filmic inner lining which conforms to the shape ofeach predefined shape of the mold. The slidable guide has also beenfound, when in use, to enable vacuum to be pulled moreconsistently/efficiently within its respective evacuatable volume. Whenmultiple elongate silicone elastomeric articles of the same length arerequired the slidable guide may be provided in a comb design used to actas the channel end and guide for the film in multiple adjacent channelsin a single mold. Preferably the slidable guides are a tight fit in eachchannel therefore acting as a barrier to prevent the escape or leakageof room temperature curable silicone composition, especially if/whenflowable, prior to curing sufficiently from its dimensionally unstableinitial form. If the slidable guide is not deemed sufficiently liquidtight a plug of suitable material may be inserted between the guide,when inserted in the mold, and the room temperature curable siliconecomposition once added into a predefined shape of the mold to avoidleakage of the room temperature curable silicone composition therefromduring the early stages of cure when potentially flowable. The plug maybe made from e.g., a fast curing 1-part silicone sealant, foam plugspreferably having closed cells and other suitable materials such asputty. The plug is introduced onto the filmic inner lining, prior tointroduction of the room temperature curable silicone composition.

In use, a film is initially draped over the mold to establish anevacuatable volume between the film and each predefined shape, e.g., achannel in the mold. The film is then drawn into each predefined shapein the mold, conforming to the mold by suction through the openingscaused by a vacuum generator resulting in the film becoming a filmicinner lining in each predefined shape in the mold conforming to theshape of the predefined shape. The use of a film in this way preventselastomer adhering to the walls of the mold during cure and consequentlypreventing damage/mechanical failure of a shaped silicone elastomericarticle upon removal from the predefined shape. The film may also beutilised to remove the resulting shaped silicone elastomeric article ora partially cured molded article out of the predefined shape in which ithas been molded.

In one embodiment the film initially draped over the mold is fixed inplace at one edge of the mold. When the film has been clamped, the firstchannel to which a vacuum is applied is that adjacent to the fixingmeans such that when suction occurs through openings in the channeldiscussed above, the film is drawn into the aforementioned channel toform a filmic inner lining which conforms to the shape thereof. Oncethis is complete in said first channel the method is repeated in theadjacent channel until suction is applied in each channel and the filmis acting as a filmic inner lining conforming to the shape of eachchannel. Once this has been completed the room temperature curablesilicone composition may be introduced into each channel. The fixing ofthe film may be undertaken by clamping the film :

a. At one extremity of the mold, or

b. Along the wall of a channel not located near the extremity of themold.

Preferably, clamping is done by use of a single clamping means along thewhole length of the mold or in the case of a series of elongate channelsalong the whole length of said first channel. Alternatively, a pluralityof clamping means may be used spaced apart along the length of the firstelongate channel, however, the former is preferred.

In one embodiment the film used for molding the elongate elastomericarticles can be used as packaging of the silicone molded part.

The room temperature curable silicone composition used herein to formelastomeric articles may be any suitable room temperature curablesilicone composition, which preferably does not contain any inorganicreinforcing filler and as such which may be flowable at the commencementof the cure process. For example, the composition utilised may be thesame or similar to those used for making spacers in WO/2018/160325 whichis incorporated herein by reference. The compositions are 2-part roomtemperature curable silicone compositions which produce suitableelastomeric articles. The room temperature curable silicone compositionmay comprise:

-   (i) at least one condensation curable silyl terminated polymer    having at least one, typically at least 2 hydrolysable and/or    hydroxyl functional groups per molecule;-   (ii) a cross-linker selected from the group of    -   silanes having at least 2 hydrolysable groups, alternatively at        least 3 hydrolysable groups per molecule group; and/or    -   silyl functional molecules having at least 2 silyl groups, each        silyl group containing at least one hydrolysable group.

(iii) a condensation catalyst selected from the group of titanates andzirconate; characterized in that:

-   -   the molar ratio of hydroxyl groups to hydrolysable groups is        between 0.1:1 to 4:1    -   and the molar ratio of M-OR functions to the hydroxyl groups is        from 0.01:1 and 0.6:1, where M is titanium or zirconium.

The composition is stored in two-parts prior to use to avoid prematurecuring and then the two-parts are mixed in a predefined ratio (e.g., aweight ratio) immediately prior to use Immediately after mixing theresulting viscosity of the composition may sufficiently low for thecomposition to be flowable. In one example of WO2018/160325, part A ofthe composition was merely a 13,500 mPa·s (at 25° C.) silanol terminatedpolydimethylsiloxane and part B of the composition or cure packagecomprised

100 weight parts of a 2,000 mPa·s trimethoxysilyl terminatedpolydimethylsiloxane (at 25° C.) and

0.3 weight parts of tetra-n-butyl titanate, per 100 weight parts of saidtrimethoxysilyl terminated polydimethylsiloxane.

Cured materials were prepared by mixing the two components of thecomposition together in a Base : curing agent weight ratio of 3:1 aftermixing in a speed mixer 4 times 30 seconds at a speed of 2300 rpm. Inthe present disclosure such a composition once mixed as described isintroduced into the predefined shapes in the mold lined with the film.

The room temperature curable silicone composition may be gunnable, i.e.,it is introduced manually or otherwise into each channel by applicationof a sealant gun. In the event the composition is introduced by means ofa robotic or other automated system the operator thereof can set theexact amount of the composition to be introduced into each channel toensure that each molded article is identical or substantially identical.This is particularly the case when the composition is flowable and assuch will flow/settle under gravity into the shape of the mold. It istherefore very important for this application to ensure that the filmicinner lining is well positioned (no clearance between film and mold) anddoes not affect the shape of the final molded article. Clearance betweenfilm and mold may result in a U-shaped cross-section, which ifsignificant, in the case of use as a spacer in an insulated glass unit,may limit contact between the spacer and the glass pane adjacent to itand as a consequence there may be mechanical failure of the spacer(adhesion failure vs. cohesive failure). In order to avoid applyingtension and stretching the film, the applied film is sucked in the moldwith vacuum and positioned channel by channel. This ensures that even ifvacuum is cut the film can remain in place and the molded article canretain its intended shape. In case the mold is made of two differentparts, place the upper part of the mold on the bottom part (base) andlock it to ensure there will not be leaks. Some molds (e.g., PVC) can bein 1 piece with the top part being fixed on the base. In that case thetwo-parts are always assembled. Prior to use the mold is placed on ahorizontal surface to ensure the room temperature silicone composition,once added is distributed evenly with a view to obtaining an elastomericarticle of a standard thickness along the whole length of the channel

In accordance with the present disclosure there is provided analternative method to extrusion, the current standard method forpreparing elongate spacer materials which is required due to the lack ofinitial structural resilience of the room temperature curable siliconecomposition used to prepare the shaped silicone elastomeric articles andthe extended cure process which takes from several hours to severaldays, e.g., seven days or more. The method herein utilises a mold and afilm to overcome the problems of preparing said shaped siliconeelastomeric articles, e.g., elongate silicone elastomeric articles froma potentially flowable room temperature curable silicone composition toform an elastomer having soft mechanical properties. When these areelongate spacers for insulating glazing units, they must have twosubstantially parallel or parallel sides, preferably of a definedlength, width and depth to concur with the dimensions required for thespacer in the insulated glazing unit and/or a combination thereof.

For this to be achieved, the two or more predefined shapes in the moldare usually in the form of a series of elongate parallel channels. Thefilm which is initially draped over the series of elongate parallelchannels is required to be drawn into each predefined shape to form afilmic inner lining conforming to the shape of the channel. The mold isdesigned so that vacuum is applied in a manner which avoids damaging orstretching the film which may cause deformation of an elastomericarticle molded therein. Deformation can occur if, for example, the filmdoes not conform exactly to the predefined shape in a mold prior tointroduction of the room temperature curable silicone compositiontherein.

It was determined that this is best achieved by applying the vacuumsequentially as described above i.e., in the case of a mold with twopredefined shapes in a first predefined shape and then when the film hasconformed to the shape of the first defined shape, maintain the vacuumin the first shape and commence the vacuum in the walls of the seconddefined shape in the mold. This means the film can slide/glide into aposition in the second defined shape to form a filmic inner liningconforming to the shape of the second defined shape withoutdamage/stretching of the film conforming to either or both definedshapes.

Hence, when the two or more predefined shapes in a mold are a series ofelongate parallel channels, say, for example, a series of seven channelswith channels being numbered from one to seven sequentially from rightto left in the mold, then the vacuum is first pulled in channel one orchannel seven. For the sake of simplicity, it is assumed that vacuum isfirst pulled in channel one. As the vacuum is pulled the film drapedover the mold is drawn into channel one to form a filmic inner liningconforming to the shape of channel one. Once this is completedsatisfactorily, the vacuum in channel one is maintained and the vacuumin channel two, adjacent to channel one is commenced and the method isrepeated until the film is satisfactorily positioned in the channels oneand two and then the method is repeated for channels three to sevensequentially such that when the vacuum is pulled in channel seven thevacuum is being maintained in the preceding six channels and the film isconforming to the shape of each of the respective channels. Once thefilm has been brought into conformance with each channel a selected roomtemperature curable silicone composition is introduced into each channelin any order in the mold.

Using this sequential application of vacuum channel by channel approachensures that even if vacuum is cut once the film is in place as a filmicinner lining of each desired shape in the mold, the film remains inplace conforming to the predefined shapes in the mold.

In the method described herein the following steps might be undertaken:-

-   -   (i) Provide a film of suitable dimensions. It should be of        proportions suitable to easily form a filmic inner lining to all        predefined shapes in the mold without the need for stretching or        damage so that it may easily conform to the shape of all the        predefined shapes. Clamp the film e.g., on the side of the first        predefined shape into which vacuum will be applied.    -   (ii) In order to avoid air leaking via the two open extremities        of the channels when vacuum is drawn, comb-like tools may be        utilised, if so one may be placed at each end of the channels in        close contact with the film thereby having the dual role of        being a film guide but also closing any air gaps which could        negatively affect the positioning of the film and drawing of the        vacuum.    -   (iii) Turn on the vacuum generator e.g., a pump or Venturi and        open a valve in said vacuum system such that suction is only        applied to the first predefined shape in the mold (i.e., first        channel). Once the suction commences the film is drawn into the        predefined shape to form a filmic inner lining which may then be        checked for any wrinkles or other defects with a view to        ensuring said first predefined shape is ready for introduction        of the room temperature curable silicone composition.    -   (iv) Once satisfied the valve in the vacuum line opening into        the adjacent second predefined shape in the mold (e.g., channel)        is also opened and the above step repeated. The same is then        completed sequentially until all the predefined shapes (e.g.,        channels) have a vacuum drawn and a respective filmic inner        lining conforming to the shapes thereof.    -   (v) If the aforementioned comb-like tool is considered not to be        sufficiently well fitting in the channels to prevent the room        temperature curable silicone composition from leaking out of the        channel into which it is supplied, a plug of suitable material,        e.g., a fast curing 1-part silicone sealant, foam plugs having        closed cells and other suitable materials such as putty.    -   (vi) Subsequent to the above the room temperature curable        silicone composition may be introduced into the predefined        shapes having filmic inner linings in the mold. The room        temperature curable silicone composition is usually stored in        two-parts prior to use to avoid premature commencement of the        cure process. The two-parts, typically referred to as part A and        part B are mixed together in the required weight ratio, using a        suitable mixer.    -   (vii) Once the room temperature curable room temperature curable        silicone composition has been mixed it is dispensed into the        predefined shapes in the mold and the room temperature curable        silicone composition is then allowed to cure.

The composition is left to cure in the mold until it is deemed to havesufficient mechanical strength to maintain its shape without the need ofthe mold any longer. This period will depend on the content of thecomposition being used to make the elastomeric articles but for acomposition that cures over say about one week the curing composition istypically left in the mold for 1 to 4 days, alternatively 1.5 to 3 daysat room temperature.

After this period the partially cured material may be removed from themold whilst retaining it in the film and the cure process is allowed tocontinue for as long as required and/or deemed necessary, again at roomtemperature.

Subsequent to completion of the cure process the resulting elongateelastomeric articles may be packaged and shipped for end use.

As previously discussed elastomeric articles prepared by the abovedescribed process are suitable as spacers in insulated glass units. Tobe suitable for use as spacers in insulated glass units the elongatearticles need to have two at least substantially parallel sides and assuch an alternative process has been developed which is suited for lowviscosity compositions requiring extended periods of time for curing.The provision of such clear spacers can significantly improve theviewing capability for a person e.g., looking into a display unit suchas a fridge. It is important that the spacer is in good contact with theglass windows as malformed rounded shapes will not adhere properly tothe glass.

A typical spacer is designed to keep two panes of glass apart and inthis disclosure, there is a strong adhesive bond between each pane ofglass and the spacer. In many warm edge type sealing solutions, aprimary sealant is required to adhere the spacer to a glass substrate.In the present case, such sealants may not be required.

If the shaped silicone elastomeric articles resulting from the method asdescribed herein may be sufficiently tacky to the touch given thepresence of excess hydrolysable groups for physical adhesion to occurwhen the substantially cured or fully cured silicone-based material isbrought into contact with a substrate surface. However, if the level ofadhesion is not deemed strong enough the substrate may be pre-treated toenhance adhesion between the shaped silicone elastomeric articlesproduced from the process herein.

The method described herein will now be described in connection with oneor more embodiments together with the Figures appended hereto. For theavoidance of doubt discussion with respect to any one particularembodiment or associated feature is not intended to be limiting thereto.The reader will appreciate that there are numerous variations andequivalents that will he made apparent from the discussion that follows.Those variations and equivalents are intended to he encompassed by thescope of the present invention as if described herein.

There follows a brief description of the figures in which

FIGS. 1a to 1c depict the stages involved in conforming the film intopredefined shapes in a mold;

FIG. 1d depicts a two-part mold;

FIG. 2 is an overhead view of a mold having seven channels with filmclamped at one edge using multiple clamps spaced equidistantly andotherwise draped over the mold;

FIG. 3 depicts an example of a comb like tool;

FIG. 4 is an end overhead view showing a mold having seven channels withfilm clamped at one edge, draped over the mold having the comb like toolin position;

FIG. 5 is an overhead view of a mold during introduction of the filminto the predefined shapes; and

FIG. 6 is an overhead view of a mold in use with the ends plugged duringthe cure of the room temperature cure composition;

FIG. 7 is an illustration of a spacer of the type which can be made bythe process herein in use spacing apart two panes of glass

Whilst each predefined shape may be the same or different for the sakeof the following description of the Figures, each predefined shape is anelongate channel in a mold having a rectangular cross-section. The moldcontains a plurality of these channels which are parallel to each otherand which are designed to produce elongate spacer materials for use ine.g., insulating glazing. It will he appreciated that such a system ismerely for example.

The Figures herein depict the stages and apparatus involved inconforming a film (2) to form a filmic inner lining in a series ofchannels (6) in a mold (4) and then molding a room temperature curablesilicone composition which may be flowable at commencement of cure,which has an extended cure time of at least several hours but typicallyseveral days, in the channels (6) previously lined with the film (2).

Initially as can be seen in FIG. la, a film (2) is draped over mold (4)comprising, in the present example, seven channels (6) to establish anevacuatable volume (8) between the film and each channel (6) in the mold(4). The channels may, for the sake of example be 2 m long, 12.5 mm wideand 18 mm deep. A series of holes (not shown) are provided in the sidewalls, corners and/or base of each channel (6). Each hole is linked to avacuum system (10) for drawing a vacuum in the respective channel (6)which is intended to draw the film (2) into the channel to form a filmicinner lining in the channel (6). The vacuum system (10) is designed sothat a vacuum may be drawn in each channel independent of whether or nota vacuum is being drawn in one or more other channels. This may beachieved by having an individual vacuum system for each channel but ispreferably operated by having a single vacuum system and a switchablevalve designed to control the vacuum drawn in each channel independentof the other channels.

The holes are dispersed across each channel in a pattern designed toensure the film (2) is made to conform to the walls of the predefinedshape without damage to the film (2), which as discussed previouslymight lead to the cure of spacer units of damaged or incorrectdimensions.

As is seen in FIGS. 1b, 1c and 2 the film (2) is clamped to one edge ofthe mold (4). Preferably, a bar (13) is fixed along the whole length ofthe first channel, as depicted by the bar (13) which in FIG. 2 is fixedin place by the approximately equidistant clamps (12).

In use, after the film (2) has been draped over the mold (4) and clampedat one edge, suction is initiated in the channel (6 a) adjacent to theclamped edge causing the evacuatable volume (8) in said channel (6 a) tobe evacuated and film to be drawn into the channel (6 a). Once the filmis lining channel (6 a) to the satisfaction of the operator, the suctionis initiated in the next adjacent channel (6 b) i.e., the second closestto the clamping means (12, 13) and adjacent to channel (6 a), whilstmaintaining the vacuum in channel 6 a. The process is repeated until thefilm (2) is lining both channels 6 a and 6 b to the satisfaction of theoperator after which the vacuum in the next channel is initiated and theprocess repeated. This happens e.g., in FIGS. lb and 2 sequentially withrespect to each channel (6) from right to left of the picture until thevacuum has been applied in all channels (6) and the film (2) is forminga filmic inner lining in each channel (6) conforming to the shape of itsrespective channel (6) to the satisfaction of the operator (FIG. 1c ) atwhich point in time the room temperature curable silicone compositionmay be introduced into the mold (4) and allowed to cure.

In one embodiment as depicted in FIG. 1d , the mold (4) may be in twoseparable parts a mold part (4 a) and a vacuum part or unit (10) suchthat while one mold (4 a) is being used solely to shape room temperaturecurable silicone composition during the curing process of several hoursto several days, it can be detached from the vacuum unit (10) providingapplication of suction is no longer required. This therefore enables thevacuum unit (10) to be reused to line a further mold (4 a) in the mannerdescribed above. It was found particularly suited to utilise thisembodiment when the mold/vacuum unit was made from metal, whilst whensubstantially manufactured in plastic the mold unit was preferably asingle unit.

It was found that in one embodiment, specific to the method when, asshown herein, the mold (4) comprises a series of adjacent, parallelchannels (6), that the introduction of a “tooth” (18) from a comb liketool (16) as depicted in FIG. 3, at each end of each channel (6) wasadvantageous. This tool (16) functioned as both a guide for the film (2)to prevent damaging the film (2) during the lining stage, but the teeth(18) thereof also acted as an end means causing an improved/consistentvacuum to be drawn in each channel (6) as and when required. Thecomb-like tool (16) may be made from any suitable material but ispreferably non-stick to the cured silicone elastomer end-product and assuch may be made from e.g., polytetrafluoroethylene (PTPB), polyvinylchloride (PVC), low density polyethylene (LDPE) or even from metals suchas steel or aluminium.

In use one tooth (18) from tool (16) is inserted into the mold (4) atthe end of each channel (6) as depicted in FIG. 4 prior to theintroduction of any vacuum to any channel (6). For the benefit of thereader FIG. 4 also depicts one potential vacuum arrangement with avacuum line (20) visible and attached to each channel (6). Such a vacuumline (20) to each channel (6) is operable by the turning of a switch toapply the vacuum in each respective channel (6). This may be automatedor may be operable manually by the operator, as required.

FIG. 5 depicts a partially evacuated mold (4) having four out of sevenchannels (6) lined by the film (2) and having vacuum applied whilst inthree channels (6) the vacuum is yet to be applied and the film remainsdraped thereon.

It was found that whilst the comb-like tool (16) is beneficial as aguide and/or as an effective end of each end of the channel (6), therebydefining the length of the elongate elastomer once the composition hascured; it was found that the teeth (18) were not necessarilysufficiently well-fitting to prevent leakage of room temperature curablesilicone composition from the mold (4) during early stages of the cureprocess when it does not have sufficient structural resilience tomaintain the shape of the channel if removed therefrom. Any suitablemeans may be utilised to prevent said leakage, however, it was foundthat one simple methodology was to introduce a plug (24) of disposablefast curing one-part sealant between tooth (18) of tool (16) and thesubsequently introduced room temperature silicone curable composition.Plugs (24) of this type are shown in FIG. 6 which depicts one end of amold during the cure process of the room temperature curable siliconecomposition.

Subsequent to the above, the room temperature curable siliconecomposition may be introduced into the predefined shapes, i.e., channels(6) in the mold (4). The room temperature curable silicone compositionis usually stored in two parts prior to use to avoid prematurecommencement of the cure process. The two-parts, typically referred toas part A and part B are mixed together in the required ratio, usuallyin a suitable two-part mixer suitable to mix low viscosity liquids (notshown), e.g., a Conti Flow Vario 2-component Mix and dispense systemfrom Reinhardt-Technik GmbH of Kierspe Germany or a Graco EFR 2-partdispensing pump from Graco Inc. of Minnesota, USA. The chosen two-partmixer is suitable to mix part A and part B at a predefined weight ratiothrough a disposable static or dynamic mixer.

Once the room temperature curable silicone composition has been added toeach channel (6), vacuum may be stopped and the room temperature curablesilicone composition left to cure in the mold for 1 to 3 days until ithas sufficient structural resilience to maintain its shape without theneed of the mold (4). This period will depend on the content of the roomtemperature curable silicone composition being used to make theelastomeric articles but for a composition that cures over say about oneweek the curing composition is typically left in the mold for 1 to 4days, alternatively 1.5 to 3 days at room temperature. If desired, theroom temperature curable silicone composition may be heated up to atemperature of about 80° C. to accelerate the cure process. After thisperiod, the partially cured material may be demolded from the mold (4)whilst keeping it in the film (2) and the cure process is allowed tocontinue for as long as required and/or deemed necessary to complete thecure process, again typically at room temperature but cure can beaccelerated by further heating up to a maximum of about 80° C.

Alternatively, the vacuum may be kept on continuously in the mold (4)for 1 to 3 days until the room temperature curable silicone compositionhas cured to an extent to have sufficient structural resilience. In afurther embodiment, it is also possible to stop vacuum temporarily (toe.g., move the mold to a storage location) and start vacuum again duringpart of the curing time. Subsequent to completion of the cure processthe resulting elongate silicone elastomeric articles may be packaged andshipped for end use.

When the elongate silicone elastomeric articles are to be used asspacers for IGUs, spacer quality may be analysed, if deemed necessary,by removing the spacer form the film, slicing a +/−1 mm piece with ablade in order to obtain a cross-section of the elongate siliconeelastomeric articles e.g., spacer. Analysis thereof may be undertakenusing an optical microscope. The vertical and horizontal clearances maybe measured, if desired. For the avoidance of doubt, “clearance” isdefined as the length of the spacer that is not conforming to the shapeof the channel in which it was cured due to constraints created byimproper film conformation on the surface of the respective predefinedshape in the mold. The surface regions which do not conform due aclearance issue will not adhere well to glass and therefore adhesiondefects may occur and the cohesive strength of the spacer on a glasssubstrate is more than likely reduced.

When the elongate silicone elastomeric articles have fully cured theymay be used as not only self-adherent pre cured silicone spacers toassemble transparent units or devices such as insulating glass units,but also in electronic displays, weather sealants, optical devices,light emitting diodes, lenses etc.

The elongate silicone elastomeric articles prepared by the enclosedmethod using compositions described in WO2018160325 will provideself-adherent transparent spacers. In some cases, the final strength ofthe transparent spacer will be sufficient for the application, whilst inothers the use of an additional structural adhesive will be required ontop and/or bottom to ensure sufficient strength of the IGU. The hightransparency of the pre-cured spacer applied using the present methodwill contribute to anaesthetically pleasing spacer which is visiblyclear.

It is to be appreciated that such transparent spacers can be used forbuilding transparent internal partitions, transparent windows and doors,especially for refrigerators, where thermal insulation is desired. Theresulting pre cured spacer produced using the method hereinbeforedescribed, can also be useful for assembling cold or hot bended glassunits, where the use of a structural spacer is a clear attribute. Iftransparent articles can be assembled, non-transparent articles can alsobe considered in combination or not with transparent articles. Thetransparent spacer may have decorative, optical and or electronicdevices fully or partially incorporated into the body of the spacerprior to curing. Said devices are then cured in the normal manner aspreviously discussed. The resulting cured transparent spacer producedusing the method hereinbefore described, will then have said devicesvisible therein or on thereon unless hidden from view behind a frame fore.g., security reasons.

The transparent structural spacer produced using the method hereinbeforedescribed, can also be useful to assemble articles, which are sensitiveto temperature, ultra-violet or liquids. It can be useful to assembleelectronic articles, optical devices, displays made of glass, metals orplastics. It is useful to assemble panels together for internalpartition in building but as well for facades and roofs. They may alsobe useful for assembling articles in appliance, automotive or aerospace,especially where transparency is desirable.

Hence, substrates which may be spaced apart by spacers produced usingthe method hereinbefore described, may include glass sheets for flatpanel displays (LED, LCD screens), glass panels for facades or cars,metal, plastic, wood, concrete or stone plates for construction,automotive, electronics etc. metal, plastic, wood, concrete fixations,like hooks, screws, nuts. If necessary, the substrates may beadditionally primed if it is necessary to physically enhance the levelof adhesion between the spacer and a substrate.

Insulated glass units may comprise one or more than one spacer. Forexample, spacers produced using the method hereinbefore described, mightbe used for articles of a unit which an opaque or coloured spacer wouldotherwise obscure but other standard spacers might be used in areaswhere the spacer material will not obscure the vision of the userlooking through the unit.

It will be noted that generally the units described are referred to asglass units, it should be understood that whilst glass has been used asan example any alternative transparent materials may be used, ifappropriate to the situation. Furthermore, in some instances theinsulated glazing unit might comprise one or more transparent panes ofglass or the like and one pane which is rendered opaque due topatterning or the like.

The present disclosure also extends to a method of making insulatedglazing units using elongate elastomeric articles as made by the methodas hereinbefore described as spacers, by providing a first pane of glasshaving a first major surface and a second pane of glass having a firstmajor surface.

Applying an elongate elastomeric article as prepared using the methoddescribed herein e.g., as an (optionally transparent) spacer onto thefirst major surface of the first glass panel.

Positioning the region of the first major surface of the second glasspanel onto the spacer and leaving the spacer to adhere to the glasssurfaces. If required, then filling a cavity around the periphery of theglass panels, with a preferably transparent secondary sealant, which maybe a moisture-curable hot melt silicone adhesive composition, saidcavity defined by the first major surface of the first glass panel,external surface of transparent spacer and the first major surface ofthe second glass panel. Alternatively, rather than a secondary sealant aprotective coating may be applied onto the outer surface of theelastomeric article/spacer to form a protective non-stick layer with aview to preventing damage to the article/spacer in use.

In one embodiment an insert made of plastic, metal, glass or the likemay be added into one or more channels before the introduction of theroom temperature curable silicone composition in order to provide theresulting elongate silicone elastomeric articles, e.g., transparentspacers with physical support that can protect the spacer from anymechanical damage in use. Such an insert may alternatively be introducedinto a channel after the room temperature curable silicone compositioneither before or during cure. This support may alternatively be providedafter cure, in which case a primer or the like may be required to obtaingood adhesion between the pre-cured spacer and the insert.

In one embodiment of the above there is provided a method of making aninsulating glass unit comprising the following steps carried out in anydesired order namely procuring two glass panes, providing between thetwo glass panes an endless strip of spacer as prepared by way of themethod hereinbefore described, urging the two glass panes towards eachother against the spacer to form a spacer adherent to the panes.

EXAMPLES

Cured materials were prepared by mixing the two components of thecomposition together in a Base: curing agent weight ratio of 3:1. Thebase component was: a 2,000 mPa·s (at 25° C.) silanol terminatedpolydimethylsiloxane. The curing agent components were:

-   -   100 weight parts of a 2,000 mPa·s trimethoxysilyl terminated        polydimethylsiloxane (at 25° C.) and    -   0.2 weight parts of tetra-n-butyl titanate.

The material was mixed in a speedmixer 4 times 30 seconds at a speed of2300 rpm and the resulting mixture was utilised as described above byaddition into the molds and then being allowed to cure for seven days.An example of the type of spacer which might be generated using themethod described above is provided as FIG. 7 which depicts two panes ofglass separated by a continuous ribbon of the cured material adhered tothe periphery of the of each glass panes effectively functioning asspacer between the two panes of glass.

The upper surface of the lower glass pane depicted and the lower surfaceof the upper glass pane may be coated with a primer type material suchas DOWSIL™ 1200 OS primer which was allowed to dry for approximately 30minutes.

A pre-measured ribbon of cured self-adhesive elastomeric article asprepared by the method as hereinbefore described was applied to theperiphery of the upper surface of the lower glass pane and subsequentlythe lower surface of the upper pane of glass was adhered to the curedmaterial in the regions previously primed. Almost immediately afterconstruction the glass unit depicted in FIG. 7 could be moved andhandled without impairing the structure of the construction because ofthe strength of the bonds formed as described herein.

1. A method for molding shaped silicone elastomeric articles from room temperature curable silicone compositions, the method comprising: (i) draping a film (2) over a mold (4) comprising two or more predefined shapes (6) to establish an evacuatable volume (8) between the film (2) and each predefined shape (6) in the mold (4); (ii) applying suction to the evacuatable volume (8) between a first predefined shape (6 a) of the mold (4) and the film (2) to establish an at least partial vacuum within the evacuatable volume (8) of said first predefined shape (6 a), such that the film (2) forms a filmic inner lining conforming to the first predefined shape (6 a) of the mold (4); (iii) additionally, applying suction to the evacuatable volume (8) between a second predefined shape (6 b) of the mold (4) and the film (2), which second predefined shape (6 b), is adjacent to the first predefined shape (6 a), to also establish an at least partial vacuum within the evacuatable volume of said second predefined shape (6 b) and consequently also forms a filmic inner lining conforming to the second predefined shape (6 b) of the mold (4); (iv) sequentially repeating step (iii) until each predefined shape (6) in the mold (4) has an at least partial vacuum within the evacuatable volume (8) thereof and the film (2) forms a filmic inner lining conforming to each respective predefined shape (6) of the mold (4); (v) introducing room temperature curable silicone composition onto the filmic inner lining conforming to one or more predefined shapes (6) of the mold (4), which composition is designed to flow sufficiently to conform to the predefined shape (6) in the mold (4) into which it has been introduced; and (vi) enabling the room temperature curable silicone composition to cure in the predefined shape (6) into which it was introduced to form a shaped silicone elastomeric article.
 2. The method in accordance with claim h wherein the predefined shapes (6) are elongate channels having a base and a first wall and a second wall, which first and second wall are substantially parallel to each other and perpendicular to the base.
 3. The method in accordance with claim 1 wherein the film (2) is fixed to one edge of the mold (4).
 4. The method in accordance with claim wherein the film (2) is clamped at either one extremity of the mold (4), or along a wall of a channel not located near the extremity of the mold (4).
 5. The method in accordance with claim 3, wherein the fixing is achieved by clamping the film (2) using a single clamp (12) along the length of the mold (4) or using a bar (13) fixed in place by a series of clamps (12) positioned equidistant from each other along the length of the mold (4).
 6. The method in accordance with claim 2, wherein the parallel walls have round edges and are designed to be greater in depth than the depth of the elastomeric article to be cured in the mold (4).
 7. The method in accordance with claim 1, wherein the mold (4) is a one part unit or is in two detachable parts, a top or mold part (4 a) and a bottom or vacuum part (10) in each case adapted such that vacuum can be effectively drawn through holes in the base and/or walls of the predefined shape (6).
 8. The method in accordance with claim 2, wherein a guide (16) is inserted at each extremity of the channels to guide the film (2) into its respective channel (6) and/or to adjust the length of one or more channels (6) in the mold (4).
 9. The method in accordance with claim 1, wherein plugs (24) are inserted into a channel (6) to prevent room temperature curable silicone composition from flowing or leaking out of the channel (6) in which it was introduced.
 10. The method in accordance with claim 1, wherein an insert is added into one or more channels (6): (i) before introduction of the room temperature curable silicone composition; (ii) after the room temperature curable silicone composition is introduced either before or during cure; or (iii) after cure, wherein optionally a primer is utilised to enhance adhesion between the pre-cured shaped silicone elastomeric article and the insert.
 11. The method in accordance with claim 1, wherein the film (2) has a thickness of from 20 to 70 μm.
 12. The method in accordance with claim 1, wherein the film (2) is selected from the group consisting of polyethylene (PE) low-density polyethylene (LDPE), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE) and fluorinated ethylene-propylene (FEP).
 13. The method in accordance with claim 1, wherein the film (2) used for molding the room temperature curable silicone compositions is also used as packaging of the silicone elastomeric articles.
 14. The method in accordance with claim 1, wherein the film (2) is treated by application of a coating or a surface treatment.
 15. The method in accordance with claim 1, wherein the room temperature curable silicone composition comprises: (i) at least one condensation curable silyl terminated polymer having at least one, optionally at least 2, hydrolysable and/or hydroxyl functional groups per molecule; (ii) a cross-linker selected from the group consisting of silanes having at least 2, optionally at least hydrolysable groups per molecule group; and/or silyl functional molecules having at least 2 silyl groups, each silyl group containing at least one hydrolysable group; and (iii) a condensation catalyst selected from the group consisting of titanates and zirconates; wherein; the molar ratio of hydroxyl groups to hydrolysable groups is between 0.1:1 to 4:1, and the molar ratio of condensation catalyst (iii) M-OR functions to the hydroxyl groups is from 0.01:1 and 0.6:1, where M is titanium or zirconium and R is an aliphatic hydrocarbon group.
 16. The method in accordance with claim 1, wherein elongate silicone elastomeric articles formed by the method are utilised as spacers in the manufacture of insulated glazing units.
 17. A shaped silicone elastomeric article obtainable or obtained by the method in accordance with claim
 1. 18. An insulated glass unit comprising a shaped silicone elastomeric article prepared by the method in accordance with claim 1, wherein the shaped silicone elastomeric article is a spacer in the insulated glass unit. 